1. Field of the Invention
The present invention relates to check valves of the type utilizing a disc or clapper as the closure member, and more particularly, to techniques for properly aligning a disc of a check valve laterally with respect to the seat in the valve body.
2. Description of the Background
Check valves having a ring-shaped body with a central fluid passageway and a disc-shaped closure member or disc are well known and preferred for many applications. A pivot pin or stem is rotatable about the valve body, and an arm interconnects the stem with the disc or clapper. The flow of fluid through the valve swings the disc and arm about the axis of the stem to open the valve, while the lack of sufficient fluid flow through the valve in a desired direction allows the disc to swing closed in sealed engagement with the valve seat, thereby prohibiting "back flow" through the line.
Many such check valves employ a sizable mechanism on one side of the valve and interconnected with the protruding stem to control and/or cushion closure of the disc. Various spring mechanisms, counterweights, and/or hydraulic or pneumatic cylinders may be used for biasing the disc toward the closed position, and for "cushioning" the closure of the disc to minimize valve and system shock damage. These mechanisms are commonly mounted on the right-hand side of the valve (looking in the direction of the oncoming fluid flow), and often require considerable spacing for field installation.
For many applications, the right-side orientation of these cushioning mechanisms presents no problems. In some applications, however, it may be preferable or necessary that the cushioning mechanism be on the left side of the valve body to facilitate installation of the valve. For these cases, special left-hand valves are normally manufactured and sold, which satisfy the installation problems but increase manufacturing and inventory costs.
Another problem associated with disc check valves involves the technique for obtaining proper lateral positioning of the disc with respect to the valve body to insure reliable sealing when the valve is closed. As used herein, the term "lateral" means the direction perpendicular to the central axis of the valve and parallel with the valve stem. For example, with the valve stem in the upper portion of the valve body and mounted so that its axis is horizontal, side-to-side or lateral positioning of the disc with respect to the seat in the valve body is required to obtain reliable sealing. Typically this lateral positioning is obtained by centering the disc with respect to the valve seat, interconnecting the axially fixed stem and the disc arm, rotating the stem and arm to mark the desired position of the arm with respect to the disc, removing the disc and drilling holes at the marked locations for receiving studs, then returning the disc to the valve body to finish assembly. This procedure is time consuming, decreases field interchangability, and is not well adapted to cost efficient valve assembly operations.
The disadvantages of the prior art are overcome by the present invention, and improved techniques are hereinafter disclosed for reliably positioning a disc with respect to a valve body for a swing check valve, and for overcoming the problems associated with manufacturing valves with cushioning devices specifically intending to be on one side of the valve body.